1. Field of the Invention
The present invention relates to a method for measuring the field strength of received signals in a time-division multiple access radio communication system, and a time-division multiple access radio communication device using the same.
2. Description of the Prior Art
In recent years, the continuing development of radio communication technology has brought many terminals to the market that use time-division multiple access radio communication system (hereinafter referred to as time-division multiple access). In conventional methods for measuring the field strength of signals received with a time-division multiple access, a measurement is performed for a certain period of time while receiving a signal at the station, and the average value is regarded as the received field strength.
The following is an explanation of a conventional method for measuring the field strength of received signals in a time-division multiple access, with reference to FIGS. 13 and 14.
In the block diagram of FIG. 13, received data is input from a received data processing path 1311 into a field strength measuring portion 1301. The field strength measuring portion 1301 measures field strengths in accordance with an external field strength measurement timing signal 1312, and outputs field strength measurement data 1313. In the timing chart in FIG. 14, a point for measuring field strength 1401 at which the field strength of the received signal is measured is decided arbitrarily within the receiving time slot of a desired station, the measurement is performed over a certain period of time starting with the timing of the field strength measurement timing signal 1312 in FIG. 13, and thus the field strength of the received signal is determined.
However, a large number of devices using this time-division multiple access leads to interference of radio waves of other stations during the time-slot for the desired station, as shown in FIG. 14. When other stations interfere during the time-slot for a certain station in conventional methods for measuring the field strength of signals received with a time-division multiple access, the field strength of signals received by the desired station cannot be measured, and the reliability of the radio communication declines.
It is an object of this invention to solve these problems, and provide a method and a device that can measure the field strength of received signals correctly, even when there is interference from other stations during the time-slot for the station employing the method.
In order to achieve these objects, the field strength of received signals are measured automatically at times when there is no interference from other stations, which is the result of a unique word detection, CRC matching or arbitrary timing with a timer.
In the following description, embodiments of the invention are directed to methods and devices for measuring field strengths of a received signal in a time-division multiple access, wherein the signal is affected by interference from other stations using the same frequency carrier wave.
According to an embodiment of this invention, a method for measuring field strength of a received signal includes the following steps: (i) detecting a unique word for a desired station in the received signal; and (ii) measuring the field strength of the received signal at a time when the unique word is detected by the detecting step (i).
According to another embodiment of this invention, the method includes the following steps: (i) ascertaining the consistency of data of the received signal by calculating and evaluating CRC in the received signal; and (ii) measuring the field strength at a time when the consistency of data has been ascertained by the ascertaining step (i).
According to a further embodiment of this invention, the method includes the following steps: (i) continuously timing a lapse of a period corresponding to an interval of time-slots for a desired station by a timer, which outputs a signal at every lapse of the period; (ii) resetting the timer to restart the timing at an arbitrary time while data is received during the time-slot for the desired station; (iii) measuring the field strength of the received signal at the time when the resetting step is performed; and (iv) repeating the measurement of the field strength of the received signal at every cycle of the time-slot, points of time for the measurement being determined in response to the output signal of the timer.
According to a further embodiment of this invention, the method includes the following steps: (i) detecting a unique word for a desired station in the received signal; (ii) ascertaining the consistency of data of the received signal by calculating and evaluating CRC in the received signal; (iii) continuously timing a lapse of a period corresponding to an interval of time-slots for a desired station by a timer, which outputs a signal at every lapse of the period; (iv) determining a time for resetting the timer, based on the result of the detecting step and the ascertaining step; (v) resetting the timer to restart the timing at the time determined by the determining step; (vi) measuring the field strength of the received signal at the time when the resetting step is performed; and (vii) repeating the measurement of the field strength of the received signal at every cycle of the time-slot, points of time for the measurement being determined in response to the output signal of the timer.
According to a further embodiment of this invention, a device for measuring field strength of a received signal includes: (i) unique word detecting means for detecting a unique word for a desired station in the received signal; and (ii) field strength measuring means for measuring the field strength of the received signal at a time when said unique word has been detected by said unique word detecting means.
According to a further embodiment of this invention, the device includes: (i) CRC calculating means for ascertaining the consistency of data of the received signal by calculating and evaluating CRC in the received signal; and (ii) field strength measuring means for measuring the field strength of the received signal at a time when the consistency of data has been ascertained by said CRC calculating means.
According to a further embodiment of this invention, the device includes: (i) a timer for continuously timing a lapse of a period corresponding to an interval of time-slots for a desired station, the timer outputting a signal at every lapse of the period; (ii) resetting means for resetting the timer to restart the timing at an arbitrary time while data is received during a time-slot for desired station; and (iii) field strength measuring means for measuring the field strength of the received signal at the time when the resetting step is performed, the measurement being repeated at every cycle of the time-slot, points of time for the repeating measurement being determined in response to the output signal of the timer.
According to a further embodiment of this invention, the device includes: (i) unique word detecting means for detecting a unique word for a desired station in the received signal; (ii) CRC calculating means for ascertaining consistency of data of the received signal by calculating and evaluating CRC in the received signal; (iii) a timer for continuously timing a lapse of a period corresponding to an interval of time-slots for a desired station, the timer outputting a signal at every lapse of the period; (iv) a microprocessor for resetting the timer to restart the timing at a time determined on the basis of the output signal of the unique word detecting means and the CRC calculating means; and (v) field strength measuring means for measuring the field strength of the received signal at the time when the resetting step is performed, the measurement being repeated at every cycle of the time-slot, points of time for the repeating measurement being determined in response to the output signal of the timer.
According to a further embodiment of this invention, a receiving device for time-division multiple access includes the device according to one of the above-mentioned embodiments; and data buffer means.
According to a further embodiment of this invention, a mobile communication terminal includes the receiving device as mentioned above.
According to a further embodiment of this invention, a mobile communication base-station includes the receiving device as mentioned above.